Why are C, C++, and LISP so prevalent in embedded devices and robots?
I once built a robot based on Java. It garbage collected right into a wall.
If you're going to have processes running that you can't micromanage (eg, a Linux based system) then they must know to yield to certain high priority processes like motion control. So either you do it yourself in a low level language like C, or you use an RTOS.
As others have pointed out already, C and C++ are used because they are low-level. Another reason for C's popularity is that just about every architecture gets a C compiler targeted for it. This is good enough for a lot of people, so extra effort isn't often put into other languages. This is sort of like saying C is popular because C is popular, but hey, that's how things work.
LISP variants are popular in robotics in part because LISP variants have historically been popular in AI research. AI is a major focus in robotics, so a lot of stuff gets carried over from that field.
LISP has been around for a long time -- 1958 according to Wikipedia. It has more history than most other high-level languages, and this has two significant implications: 1) LISP is more firmly established (in the areas it is commonly used) than other high-level languages and 2) LISP interpreters have already been made to run on all manner of resource-limited hardware (see the next bullet point).
Interpreters are easier to implement for LISP variants than for many other high-level languages, and they can be made reasonably efficient. Scheme, for example, is a really easy language to parse, both conceptually and in CPU exertion.
To see why other languages do not have a strong foothold in embedded programming, just take the converse of the reasons that C, C++, and LISP do have a strong foothold.
They are not already popular in this field, so effort is not put into supporting them.
They were not used by previous generations, so newbies are not taught to use them.
They don't have much history (in this field). They represent the unknown. The unknown is scary (and hard).
They are taxing on limited hardware.
NOTE: When I talk about limited hardware, this is what I mean: a lot of embedded work still involves systems with between 256 bytes and 32 kiB of RAM. A smart phone that has 128 MiB of RAM is not a limited system.
Because embedded devices mostly have limited resources where it is not welcome to have luxury such as automatic garbage collector. C/C++ allows you to work on quite low levels and program close to machine so that you get effective code as very much needed on those devices.
One more area where high-level languages like Java and .NET don't play well is real-time operation. You can't afford to get suddenly stalled because the garbage collector just kicked in at the worst possible moment.